Excerpts from Books and Wikipedia
"The highest levels of trauma centers have access to specialist medical and nursing care, including emergency medicine, trauma surgery, critical care, neurosurgery, orthopedic surgery, anesthesiology, and radiology, as well as a wide variety of highly specialized and sophisticated surgical and diagnostic equipment. . . . A Level I trauma center provides the highest level of surgical care to trauma patients. Being treated at a Level I trauma center can reduce mortality by 25% compared to a non-trauma center. It has a full range of specialists and equipment available 24 hours a day and admits a minimum required annual volume of severely injured patients." [Wikipedia: Trauma center; Also see Wikipedia: List of trauma centers in the United States]